Yes, I did read the whole thread, how could a restate whitout reading the
whole thread.
The "restate" is also the way a do measure S-parameters.
And I did say you need an angle also.
reflection coefficient = Vreflected/Vincident = polar magn. and angle
Whit angle I mean Phase Shift.
If you can measure polar magn. and angle, there is no need to go MUCH
deeper.
The fact you did go much deeper is? Use of analog equipment.
The question was, instead of use VNA, use oscilloscoop?
Lissajous figures measurement method is very basic stuff, its stated in my
scopes
manuel.
Work with complex numbers and Smith Chart is a hobby of me, so I know too
what is a "complex load".
How to construct a direction coupler, stripline, any impedance, frequency,
even a
direction coupler for every frequency if you only have to measure phase
shift.
To measure the magn. I use the bridge of Wheatstone, with a zero biassed
Schottky detector diode DVM and some formules.
To give 40,000 $ for a VNA is one way, do it with "things" around you with
the
same results, Hey isn't that homebrew?
I don't think there is anything I can't measure, even noise density ! If it
can't be
measured, I can calculate it.

Now the purpose for my reaction was, that you where going to think, hey
dummy
HOW did you do it?
Instead of that you did reply, we where MUCH deeper....
That's the way (maybe a little unfair) I did reply, did I miss something?
I learnt that you should not trough your self away, someone else will do it
for you !

BTW the scope is limited to 1Ghz, digital, full of wave calculations,
anything you name.

Man... did you hurt me MUCH !

Would this be the end of this thread, a would not hurt anyone.
Maybe I should have not reply at all, I choose the wrong "entry".





"Steve Nosko" schreef in bericht
...

"bviel" wrote in message
...
Use a direction coupler for forward and reverse measurement.
Use a 2 Chan. Scope great bandwith not nessesary, it is the amplitude
that
is to be measured.
reflection coefficient = Vreflected/Vincident = polar magn. and angle
Chris Bowick Book page 104, reflection coefficient may be plotted
directly
in the Smith Chart, and the corresponding impedance read off the chart.
Or did I missed something?

Yup, much of what was said. You simply restated it, to some degree. We
were MUCH deeper...way past the basics.

The scope has to work reasonably well at the frequency of interest. They
can die pretty fast abofe their useful frequency.

You also have to measure *phase* between the two signals.
--
Steve N, K,9;d, c. i My email has no u's.





"Joe Rocci" schreef in bericht
news:T0eSc.4297$Kv2.4186@trndny09...
Steve,
A decent (not the dollar store variety) CATV splitter has directivity
of
about 30 dB from 5Mhz to over 500 MHZ. I think this would do the job.

Joe
W3JDR


Steve Nosko wrote in message
...

"Paul Burridge" wrote in message
...
On Tue, 10 Aug 2004 01:53:44 GMT, "Joe Rocci"
wrote:

Here's an idea that's just whacky enough that it might work...has
anyone
tried it?

If you have a dual-trace scope with enough bandwidth, you might
be
able
use
Lissajous patterns. The idea would be to drive the complex load
through
a
directional coupler with fairly good directivity. A sample of the
incident
signal would go into the scope X input and a sample of the
reflected
signal
would go into the Y input. With a pure reactance as a calibration
load,
adjust the X and Y scope gain for a perfect circle on the
display.
Replace
the test load with a complex load, and the magnitude and
inclination
of
the
line/oval display can tell you amplitude and phase of the
reflected
signal,
from which any other metric can be calculated.

Nice idea, Joe! If it could only be made to work, you'd be a
genius.
--


OK Actually, this looks good as long as you have a directional
coupler
for
the frequency of interest! Paul didn't say. (SWR Bridge, actual
bridge,
for lower frequencies) You'll also have to allow for the difference
in
location of the two samples by adjusting the line lengths to the two
scope
probes intil they are both at the same "distance" from the load.
Judging
phase shift from a circle can't be as good as simply looking at the
two
waveforms. The scope horiz gain can be adjusted for some nice
number
of
divisions for each half cycle, say 9...
I've got a 100MHz. dual trace storage scope, but any directional
couplers around here only will be down to 130 Mhz at best... I do
also
have
a good bridge for down to 5 MHz., (also about 1 meter worth of
stretch
line...so it is possible as long as the power level is within the
bridge
capability.
--
Steve N, K,9;d, c. i My email has no u's.